Re: [PATCH] rcutorture: Avoid problematic critical section nesting on RT

On 2021-08-19 22:23:37 [-0500], Scott Wood wrote:

On Tue, 2021-08-17 at 16:40 +0200, Sebastian Andrzej Siewior wrote:

quoted

[bigeasy: remove 'preempt_disable(); local_bh_disable(); preempt_enable();
 local_bh_enable();' from the examples because this works on RT now. ]

Does it actually work?  If preemption is disabled during local_bh_disable,
softirq_ctrl.lock won't be taken.  If you then get preempted between the
preempt_enable() and the local_bh_enable(), and another task tries to do
local_bh_disable(), won't it successfully get softirq_ctrl.lock, add to
softirq_ctrl.cnt, and proceed right into the critical section?

Or am I missing something?

No, I mixed it up with migrate_disable/enable. I corrected it while
redoing it yesterday.

-Scott

Sebastian